Rapidly repositionable powered support arm

ABSTRACT

A repositionable, lockable support arm assembly for surgical and other tools includes a base arm having a lower end and an upper end, a distal arm having a proximal end and a distal end, and a central joint, typically a rotational joint, directly or indirectly linking the upper end of the base arm to the proximal end of the distal arm. A lower joint, typically a spherical joint, is positioned at the lower end of the base arm, and an upper joint, also typically a spherical joint, is located at the distal end of the distal arm. A locking mechanism is coupled to the base arm at a location above the lower joint and is configured to simultaneously deliver locking forces to the lower joint, to the rotational joint, and to the upper joint. The kicking mechanism usually includes a powered, bilateral force generator for actuating the locking mechanism.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the following provisional patentapplications: (1) 62/139,535 (Attorney Docket No. 49053-703.101), filedon Mar. 27, 2015; (2) 62/169,440 (Attorney Docket No. 49053-703.102),filed on Jun. 1, 2015; (3) 62/213,509 (Attorney Docket No.49053-703.103), filed on Sep. 2, 2015; and (4) 62/280,631 (AttorneyDocket No. 49053-703.104), filed on Jan. 19, 2016. The full disclosuresof each of these prior provisional applications is incorporated hereinby reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates generally to apparatus and systems forsupporting surgical and other tools. In particular, the presentinvention relates to lockable, articulated arms for supporting surgicaland other tools.

In many industrial and medical applications, it is desired to have arepositionable, low-profile arm capable of securing and supportingobjects in space. For example, in the field of surgery, it is common formultiple instruments and retractors to be used simultaneously fordifferent purposes including exposure and visualization of the surgicalsite as well as performing a desired procedure. Since the surgeon cantypically hold and manipulate only one instrument in each hand, surgicalassistant(s) and/or repositionable support arms are often used to holdadditional instruments. Since additional personnel are costly, crowd theoperating area, and have difficulty holding instruments steady over longtime periods, repositionable support arms are an attractive option.

Most repositionable support arms used in surgery include two or more armsegments held together by joints that are locked and unlocked by thesurgeon or assistant using one or more threaded knobs or levers. If thejoints are not tightened sufficiently, the instruments can “drift” whichat a minimum is an inconvenience and can sometimes present a significantrisk to the patient. While simple in theory, in practice it can bedifficult to apply the necessary force to the locking knob or leverwhile simultaneously holding the instrument steady at a desired placeand orientation. Another challenge in using conventional repositionablesupport arms is that two hands are required: one to hold the instrumentand another to tighten the knob(s) or lever(s) A third challenge is thatthe process of unlocking the arm, re-positioning the instrument, andretightening the arm is cumbersome and takes valuable time away from theoperation.

To partially address these challenges, repositionable support arms havebeen proposed that use a push button or switch to control a power supplyor stored energy source (e.g. compressed gas) to lock the arm joints.Such arms can be rapidly locked and unlocked, making the instrumentrepositioning task less cumbersome. To date, however, such poweredrepositionable support arms have been bulky, expensive, difficult tosterilize, and prone to joint slippage due to low joint locking forces.

Thus, it would be useful to provide repositionable, lockable supportarms for surgery and other purposes that offer one or more of rapidadjustability and instrument placement, one-handed operation, high jointlocking forces and instrument stability, compact profile, simplesterilization, and low cost. The present invention preferably providesat least some of these objectives.

2. Background Art

Relevant background patents include: U.S. Pat. Nos. 4,402,481;4,606,522; 6,491,273; 3,910,538; 6,575,653, 3,858,578; and 5,020,933.

SUMMARY OF THE INVENTION

In a first aspect, the present invention provides a lockable,repositionable support assembly comprising a base arm having a lower endand an upper end, a distal an having a proximal end and a distal end, acentral joint directly or indirectly linking the upper end of the basearm to the proximal end of the distal arm, a lower joint at the lowerend of the base arm, an upper joint at the distal end of the distal arm,and a locking mechanism (typically including an actuator as describedbelow) coupled to the base arm at a location above the lower joint andconfigured to simultaneously deliver locking forces to the lower joint,to the center joint, and to the upper joint. By “above,” it is meantthat the locking mechanism is on a side of the lower joint which isdistal the lower joint, i.e. in the direction toward the center joint.The lower joint of the lockable support assembly will typically beconfigured to be removably attached to a surface such as a side rail ona surgical bed, often indirectly by a pole or other intermediate supportelement. The upper joint will typically be configured to removablyattach a tool or tool holder for surgery or other purposes.

The joints may have any configuration of a type used in lockable,repositionable support assemblies, typically being spherical or balljoints which provide a “universal” pivoting motion in three-dimensionspace, rotational joints which provide rotation in a plane relative toan axis, translational joints which allow movement along a straight,curved or other line, and the like. In the specific embodiments, thecentral joint is usually a rotational joint while the upper and lowerjoints are typically spherical joints.

The locking mechanism of the present invention may also have a varietyof configurations. Suitable locking mechanisms will typically deliverlocking forces by at least one of compression (e.g. pushing), tension(e.g. pulling), rotation, or combinations thereof. The locking forceswill engage or interact with the joints to selectively immobilize thejoints which in turn will hold or lock the joints and arms in a desiredposition. When the joints are free of locking forces, the joints andarms will be manually repositionable so that a user can place a tool,instrument or other article held at the distal end of the distal arm ina desired location and orientation, and after the position issatisfactory, apply the locking force to immobilize the arm and hold thetool or instrument in place until the arm is released.

In specific embodiments, the locking mechanism comprises a “powered”bilateral force generator which transmits a locking force in one axialdirection to the lower joint and in an opposite axial direction to thecentral joint and the upper joint. The locking mechanism will usuallycomprise an upper base rod which transmits the locking force from oneside of the bilateral force generator to the central joint and a distalrod which transmits the locking force from the central joint to theupper joint. The locking mechanism may further comprise a lower base rodor extender which transmits force from an opposite side of the bilateralforce generator to the lower joint. Alternatively, the lower ball jointmay be coupled directly to the opposite side of the bidirectional forcegenerator. In the illustrated embodiments, the bilateral forcegeneration may be fluidically powered, e.g. hydraulically and/orpneumatically, or may be electrically powered.

The term “rod,” as used herein, includes any elongate structure ormember having an axis and being capable of transmitting mechanical forcevia compression (e.g. pushing in the axial direction), tension (e.g.pulling in the axial direction), and/or rotation about the axis. The rodis illustrated as a simple cylindrical elongate element, but may haveother geometries, such as beams having rectangular or other non-circularcross sections, and the like. The rods will usually be formed in onepiece but could also be formed with two or more segments joined togetherto transmit the desired force. Usually, the rods will be rigid but insome cases could be non-rigid, e.g. when used for applying tensionbetween joints or other elements.

In fluidic embodiments, the bilateral force generator comprises ahydraulic or pneumatic driver with a piston which travels in a firstaxial direction and a cylinder or a second piston which travels in asecond axial direction. The driver is axially aligned with the base armso that the piston is disposed to transmit locking force in one axialdirection along the base arm, e.g. to the central joint, and thecylinder or second piston is disposed to transmit locking force in theother axial direction, e.g. to the lower joint. The fluidic bilateralforce generators will usually also include a fluidic generator, e.g. agenerator which produces pressurized hydraulic or pneumatic fluid. Thefluidic generator will typically be located remotely from the hydraulicor pneumatic driver and will be connected to the driver by fluidicconnecting lines.

In electrically powered embodiments, the bilateral force generator maycomprise an electric motor and a force multiplier means. The multipliermeans may comprise a lead screw driven by a motor and a follower whichtravels over the screw. Alternatively, the multiplier means may comprisea mechanical linkage consisting including two links coupled togetherwith three pin attached in-line with the upper base rod. Othermultiplier means include a combination of a gear reduction, a screwdrive, a rack-and-pinion drive, or a roller-wedge mechanism.

In other specific embodiments, the central joint comprises a rotationaljoint having an axle joining the upper end of the base arm to theproximal end of the distal arm and wherein an interface surface at theupper end of the base arm frictionally engages an interface surface onthe proximal end of the distal arm such that the locking mechanismdrives the interface surfaces together to prevent relative movement ofthe arms. Such rotational joints may further comprises a first inclinedsurface which receives force from the upper base rod and a secondinclined surface which transmits force to the distal rod, wherein thealigned surfaces are coupled by the axle which both (1) locks theinterface surfaces together; and (2) translates the second inclinedsurface in response to the upper base rod engaging the first inclinedsurface. The upper and lower joints may each comprise spherical jointsincluding a friction block which is coupled to the bilateral forcegenerator to lock the spherical joint when the generator generates alocking force or is otherwise actuated.

The lockable, repositionable support assemblies of the present inventionalso allow for convenient draping, sterilization, and replacement of thesterilized components. In particular, the lockable support assemblies ofthe present invention may comprise a base arm which is separable fromthe locking mechanism to allow removal of the base arm, distal arm, andcentral and upper joints to permit sterilization or replacement of thebase arm, distal arm, and central and upper joints.

A lockable support system may comprise the lockable support with asterile drape configured to cover the locking mechanism when the basearm, distal arm, and joints are connected to the locking mechanism.

In a second aspect, the present invention provides a lockable supportassembly comprising a base arm having a lower end and an upper end, adistal arm having a proximal end and a distal end, a center jointdirectly or indirectly linking the upper end of the base arm to theproximal end of the distal arm, a lower joint at the lower end of thebase arm, an upper joint at the distal end of the distal arm, a poweredlocking mechanism configured to simultaneously engage the lower joint,the center joint, and the upper joint to deliver locking forces to saidjoints to prevent relative motion of said arms, and a latching mechanismwhich prevents the arms from moving and/or prevents the lockingmechanism from disengaging the joints upon loss of power to the lockingmechanism.

The locking mechanism typically comprises a force generator whichtransmits a locking force through the base arm and the distal arm tolock the joints, and the force generator usually comprises a fluidicdriver, e.g. hydraulic or pneumatic, with at least a first piston whichtravels in a first direction and a second piston or cylinder whichtravels in an opposite direction to transmit the locking force.Alternatively, the force generator may comprises a motor which iscoupled by a force multiplier to deliver forces to the center, lower andupper joints.

The latching mechanism may comprise a spring-loaded element which isconstrained while the assembly is receiving power and which is releasedfrom constraint to latch the locking mechanism and/or arms when power islost. Alternately, the latching function may be provided by thenon-reversible nature of the force multiplier.

In a third aspect, the present invention provides a lockable supportassembly comprising a base arm having a lower end and an upper end, adistal arm having a proximal end and a distal end, a center jointdirectly or indirectly linking the upper end of the base arm to theproximal end of the distal arm, a lower joint at the lower end of thebase arm, an upper joint at the distal end of the distal arm, a poweredlocking mechanism configured to simultaneously engage the lower joint,the center joint, and the upper joint to deliver locking forces to saidjoints to prevent relative motion of said arms, wherein the arms remainlocked when the powered locking mechanism loses power; and an overridemechanism to permit manual repositioning of the arms upon loss of powerto the locking mechanism.

The override mechanism temporarily disengages the locking mechanism topermit manual repositioning and relocking of the arms when the poweredlocking mechanism loses power. The force generator may comprise ahydraulic or pneumatic cylinder with at least a first piston and asecond piston or a cylinder which travel in opposite directions totransmit the locking force. The force generator may comprise a motorwhich is coupled by a force multiplier to deliver forces to the center,lower and upper joints, wherein the override mechanism disengages thelead screw.

In a fourth aspect, the present invention provides a lockable supportassembly comprising a base arm having a lower end and an upper end, adistal arm having a proximal end and a distal end, a center jointdirectly or indirectly linking the upper end of the base arm to theproximal end of the distal arm, a lower joint at the lower end of thebase arm, an upper joint at the distal end of the distal arm, and apowered locking mechanism configured to simultaneously engage the lowerjoint, the center joint, and the upper joint to deliver locking forcesto said joints to prevent relative motion of said arms, wherein at leastsome of the joints are biased to eliminate or reduce clearances in thejoint or locking mechanism in the absence in the absence of lockingforces to prevent an unintended change of arm position when as thelocking mechanism engages the joints.

The locking mechanism may comprise a force generator which transmits alocking force through the base arm and the distal arm to lock thejoints, and the force generator may comprise a fluidic (e.g. hydraulicor pneumatic) cylinder with at least a first piston and a second pistonor a cylinder which travel in opposite directions to transmit thelocking force. Alternatively, force generator may comprise a motor whichis coupled by a force multiplier to deliver forces to the center, lowerand upper joints.

In another aspect of the present invention, the locking arm assembly mayfurther include a lock/unlock button or switch disposed near a distalend of the distal arm to enable one-handed instrument manipulation andunlocking/locking. The lock/unlock button or switch may be configured toinitiate or enable operation of the any of the locking mechanismdescribed and claimed herein.

In still another aspect of the present invention, locking forces may betransmitted substantially simultaneously to the lower joint, centerjoint and upper joint using mechanical elements.

In yet another aspect of the present invention, the base, the distalarm, the central joint, the lower joint, and the upper joint areconfigured to be driven solely by the locking mechanism and the lockingmechanism is powered by a single connector. This is advantageous as thelockable support assembly does not have to interface with other powersources external to the assembly. Elimination of such interfaces isbeneficial to improve clinical workflow, and is made possible by theefficient power utilization of the lockable arm of the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a repositionable, lockable support arm constructed inaccordance with the principles of the present invention incorporating anelectric locking mechanism.

FIG. 2 shows a repositionable, lockable support arm constructed inaccordance with the principles of the present invention incorporating afluid powered locking mechanism.

FIG. 3 is an enlarged view of the components in a portion of FIG. 2.

FIG. 4 is a cross-sectional view of the components of FIG. 3.

FIG. 5 is a detailed cross-sectional view of a distal joint on a distalend of a distal arm of FIGS. 1-4.

FIG. 6a-6h are detailed cross-sectional views of the central rotationaljoint of FIGS. 1-4.

FIG. 7 is a detailed cross-sectional view of the electric lockingmechanism of FIG. 1.

FIG. 8 is a detailed cross-sectional view of the fluid locking mechanismof FIG. 2.

FIG. 9 shows a cross-sectional view of a master fluid cylinder assemblythat drives the fluid locking mechanism of FIG. 8.

FIG. 10 shows a schematic of a pneumatic system that provides power tothe master fluid cylinder assembly of FIG. 9.

FIG. 11 shows a cross-sectional view of an alternate bilateral lockingmechanism embodiment powered directly by pressurized fluid withactivation valve adjacent to the fluid piston.

FIG. 12 shows a cross-sectional view of an alternate bilateral lockingmechanism embodiment powered by two opposing pistons.

FIG. 13 shows a cross-sectional view of an alternate bilateral lockingmechanism embodiment powered by a single piston and movable cylinder.

FIGS. 14(a)-(b) show a roller ball joint that provides a mechanicalmeans for forcibly separating two bodies as an alternative to use ofpistons in the locking mechanisms of FIG. 8 and FIGS. 11-13.

FIG. 15 shows a cross-sectional view of an alternate bilateral lockingmechanism embodiment using linkage members and an eccentric hub togenerate mechanical advantage.

FIG. 16 shows a cross-sectional view of an alternate bilateral lockingmechanism embodiment that uses roller wedges to create mechanicaladvantage.

FIG. 17(a)-(d conceptually shows different ways for the lockingmechanism to distribute locking force to the arm joints.

FIG. 18a shows a cross-sectional view of a center rotational joint thatis locked by pulling the upper base rod in a direction away from thecenter rotational joint.

FIG. 18b shows a cross-sectional view of a center rotational joint thatis locked by rotating the upper base rod.

FIG. 19 shows a cross-sectional view of a spherical joint that is lockedby pulling an inner rod in a direction away from the spherical joint.

FIG. 20 shows a cross-sectional view of an alternate locking mechanismthat exerts locking tension forces on an outer arm segment.

FIGS. 21a-d show cross-sectional views of alternate embodiments of thecenter rotational joint of FIGS. 1-4.

FIGS. 22a and 22b shows alternative embodiments of the proximal portionof a repositionable, lockable support arm where the locking mechanismlatches and is located at the base of the arm. FIG. 22a is a perspectiveview and FIG. 22b is a cross-sectional view.

FIG. 23 is a cross-sectional view of an alternative embodiment of thecenter rotational joint of FIGS. 1-4 where rolling elements are used toreduce frictional energy losses.

FIG. 24 is a cross-sectional view of an alternative embodiment of thecenter rotational joint of FIGS. 1-4 where roller wedges are used toreduce frictional energy losses and generate mechanical advantage.

FIG. 25a-h show cross-sectional views of various embodiments forpreloading the joints of a repositionable, lockable support arm. FIGS.25a-f show preloading embodiments with a spring located at the centerrotational joint, and FIGS. 25g-h show preloading embodiments with aspring located at the base spherical joint and/or distal sphericaljoint.

FIG. 26a-b show cross-sectional views of two alternative embodiments formechanical override lock/release systems for a repositionable, lockablesupport arm.

FIGS. 27a and 27b show an alternative embodiment for a locking sphericaljoint with increased range of motion that may be combined with arepositionable, lockable support arm in accordance with the presentinvention. FIG. 27a shows a 3D view and FIG. 27b shows a cross-sectionalview.

FIGS. 28a and 28b show two embodiments for sterilization systems for arepositionable, lockable support arm in accordance with the presentinvention.

FIGS. 29a and 29b show a detailed embodiment of an interface to attachand remove the distal arm from the locking mechanism as depicted in FIG.28 b.

FIG. 30 shows an embodiment for a proximal arm linkage counter balancesystem for use in a repositionable, lockable support arm in accordancewith the present invention.

FIG. 31 shows an alternate octahedron embodiment for a proximal armlinkage counter balance system for use in a repositionable, lockablesupport arm in accordance with the present invention.

FIGS. 32a and 32b show a retraction system comprised of multiplerepositionable, lockable retractor support arms in accordance with thepresent invention.

FIG. 33 shows an instrument positioning system with increased strengthand stability by operating multiple repositionable, lockable supportarms in parallel.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a repositionable, lockable support arm constructed inaccordance with the principles of the present invention in use in asurgical procedure on a patient (11). An electric base unit (1) clampsto the railing (2) of a surgical table (3). A manual clamp (4) on thebase unit tightens the base unit (1) against the railing (2) and enablesadjustment of a pole (5) that determines the height of the arm above thesurgical table. The arm itself consists of an electric actuator unit (6)near the proximal base, a base arm segment (7), and a distal arm segment(8). An instrument holder (9) connects an instrument (10) to the distalend of the arm. A lock/unlock button (12) is provided on or near theinstrument holder so that a user can initiate power locking andunlocking of the arm with the same hand that positions and/or holds theinstrument at a desired location and orientation relative to the patient(11). In FIG. 1, the joints are locked and unlocked with an electricbase unit (1) and an electric bilateral actuator (6), as furtherdescribed with reference to FIG. 7 below. In FIG. 2, the joints of thearm are locked and unlocked with a fluid system consisting of a fluidbase unit (20) and a fluid bilateral actuator (21), as further describedwith reference to FIGS. 8-10 below.

The locking arms of FIG. 1 and FIG. 2 comprise a serial linkage of armsegments joined by spherical and rotational joints. As shown in moredetail in FIG. 3, the base arm segment (7) and distal arm segment (8)are connected with a central rotational joint (30). A base sphericaljoint (31) is held in a base sphere retainer (35) located at a proximalor “base” end of the actuator unit (400) which is connected to aproximal end of the base arm segment (7). A distal spherical joint (32)is held in a distal sphere retainer (36) located at the distal end ofthe distal arm segment (8). An additional distal rotational joint (33)may be provided between the distal spherical joint (32) and centralrotational joint (30) to permit rotation of the distal sphere retainer(36) with respect to the distal arm segment (8). Similarly, a rotatablebase joint (34) may be provided between the proximal end of the base armsegment (7) and the actuator (400) to enable rotation of the base armsegment (7) with respect to the base sphere retainer (35). In somepreferred embodiments the spherical retainers have a slot (37) whichallows for extended pivoting of the spherical joint in the slot.

While only base and distal arm segments are illustrated in FIGS. 1-3,additional “intermediate” arm segments could be provided between thecentral rotational joint (30) and the distal sphere retainer (36) sothat the central rotational joint links the upper end of the base arm tothe proximal end of the distal arm “directly or indirectly.” Eachadditional arm segment would usually require at least one additionaljoint, usually one additional rotational joint, to be added to form arepositionable, lockable support arm structure. Such additional armsegments can provide greater coverage and ability for the arm bepositioned with more degrees of freedom in the surgical field.

Referring now in particular to FIG. 4 and FIG. 5, locking forces aretransmitted “bi-laterally” in proximal and distal directions from thebilateral actuator (400) as indicated by arrow (6 a). A distal rod (41)and an upper base rod (42) extend through axial passages in the base armsegment (7) and the distal arm segment (8), respectively, and transmitthe locking forces in a distal direction to the central rotational joint(30) and the distal spherical joint (32). A proximal force from theactuator (400) is transmitted by an extender (6 e) at a proximal or baseend of the actuator (400) to lock the base. Compressive loads on thedistal rod (41), the upper base rod (42) and extender (6 e) push on thespherical joint friction blocks (43) (44) which apply pressure to bothspherical joints (31) and (32) substantially simultaneously. Thecompressive loads on the extender (6 e) result from expansion of theactuator (400) which is in contact with the extender. The compressiveloads on the inner rods cause reaction forces (extensive loads) throughthe base and distal arm segments (7) (8). These reaction forces aretransmitted through a base and distal ramped interface (39) (38) betweenthe arm segments (7) (8) and the sphere retainers (35) (36), thusapplying frictional forces at the ramped interface and locking the baseand distal rotational joints (34) (33). While Figure S shows the distalor upper spherical joint (32), the details are similar for the basespherical joint (31).

FIG. 6a shows the center joint (30) in more detail and illustrates howlocking forces are transmitted from the upper base rod (42) in the basearm segment (7) to the distal inner rod (41) in the distal arm segment(8). The center joint (30) defines a motion/force transfer mechanismthat receives a locking force from the upper base rod (42) andsimultaneously applies the locking force to the center joint itself andto the distal rod (41). This transfer mechanism includes a base slug(60) and distal slug (61). A ramp interface (42 r) on the distal end ofthe upper base rod (42) pushes against a ramp interface surface (60 r)on the base slug member (60) as the upper base rod (42) is pushed upwardby the actuator (400) (FIG. 4). The angle of the ramp interface surface(60 r) causes the base slug (60) to translate laterally away from thebase side of the arm in the direction of arrow (60 a). A capped axlemember (63) connecting the base slug (60) and distal slug (61) causesthe distal slug (61) to translate medially towards the base side of thearm in the direction of arrow (61 a). As the distal slug (61) translatesmedially, a distal ramp interface (61 r) engages a ramp interface (41 r)on the distal rod (41) to push the rod in the direction of the distalspherical joint (32). A distal end of the distal rod (41) pushes thefriction block against the ball of the distal spherical joint (32),locking the distal spherical joint (32) in place. FIG. 6b is a detailedcross sectional view of the distal ramp interface.

Referring back to FIG. 6a , when the distal slug (61) translatesmedially, the distal ramp interface (61 r) causes a medially-directedforce to be applied between the distal inner rod (41) and the distal armsegment (8). This force causes the entire distal half of the arm toexert a force on the base half of the arm at the central rotationaljoint interface, thus applying a locking force to the central rotationaljoint (30). A friction washer (67) at the central rotational jointincreases the central rotational joint locking torque. Note that, bydesign, the system has small clearances between moving parts. As aresult, only a small magnitude of motion (typically less than 2 mm) ofthe actuator can move the system between the locked and released state.

Another feature depicted in FIG. 6a is a manual lock and unlock backupor override mechanism for use in case of actuator failure. A threadedknob (66) is placed over a threaded shank of the axle member (63). Theknob can be turned to increase or decrease a locking force on the baseslug (60) and distal slug (61) which in turn tightens or expands thecenter joint, thus manually locking or unlocking the entire armindependent of the state of the actuator. Such manual locking featurescould be placed anywhere along any of the members in the clamping path(refer forward to FIG. 26). Axle member (63) may have a key restrictingits rotation relative to the base slug (60). In the embodiment shown alocking nut (68) is affixed onto the axle. The axial clearance (68 c)between the knob (66) and the nut (68) provides a limited range ofmotion of the knob. This motion may correspond to the actuation rangeensuring that the joints are not too loose nor may not be overtightened. In another embodiment, instead of a knob (66), there may bean interface that requires a tool to operate. This prevents accidentaloperation of the knob.

Actuators of many sorts are known to one skilled in the art. In apreferred embodiment of the invention, the actuator (400) has theproperty of being “normally on” That is, if actuator power is lost whilethe arm is locked during a medical procedure, the arm will remain lockedsuch that the instrument being held does not lose its position.Unexpected unlocking of the an can have serious medical consequenceswhen the instrument being held is in a delicate or sensitive positionwith respect to the patient (for example, a trans-nasal endoscope usedfor visualization during pituitary brain surgery). Therefore in oneembodiment of the invention, the actuator is powered electronically witha non-backdrivable force multiplier.

Referring to FIG. 7, an electric bilateral actuator (6) generallycomprises a lead or drive screw driven by a motor and a nut or otherfollower which travels over the screw. A specific embodiment is shown incross section. A motor (70) with planetary gearhead (71) turns a gearboxshaft (71 s) coupler rigidly attached to a lead screw body (72).Rotation of the lead screw causes a lead nut (73) to translate withrespect to the shaft assembly, compressing the upper base rod (42) andmotor cage (75). Flanges (not shown) on the lead nut and motor mountconstrain motion to pure translation and prevent the lead nut fromrotating with respect to the assembly. A thrust bearing (74) supportsthe large compressive loads. The motor transmission design (gearbox andlead screw) can be selected to prevent “back driving” of the gears whichis advantageous because the actuator will remain in its current state inthe event of a power or motor failure, and thus the arm remains in itscurrent state (locked or unlocked). In alternate embodiments, the leadscrew may be replaced with alternate multiplier means may include acombination of a gear reduction, a differential screw drive, arack-and-pinion drive, worm gear drive, a roller-wedge mechanism, rollerball mechanism (FIG. 14), or other means.

To drive the system and lock with a particular force, a particulartorque must be applied to the motor. Since current is proportional totorque, by precisely limiting the maximum current during the lockingphase, a particular joint locking force can be achieved. Since maximumcurrent can be software-selectable using a current sensor, the lockingforce can be software-selectable in this embodiment. Current can beconveniently drawn from a battery that is located in the base unit ofthe arm (1), thus making the system a self-contained unit andeliminating the need to plug in external cords.

When the nut (73) is returning to its “home” proximal position (76), acontact switch (not shown) can be used to shut the motor off before ithits the “hard stop” at its home position, thus preventing motor damageand limiting “shock loads” on the system. In another embodiment, a stiff“crash spring” (not shown) can be provided at the home position (76).This spring may be a rubber disk, ceramic brake disk, Belleville diskspring, or other material.

In another embodiment of the invention, the bilateral actuator ispowered with fluid (preferably hydraulic fluid). This is depicted incross section in FIG. 8. The actuator includes an outer case (81) whichis rigidly connected to the base sphere retainer. Inside this case isthe actuator cylinder body (82) that is free to move axially inside thecase. The actuator body is rigidly capped at the ends by an upper cap(83) and lower cap (84). Disposed inside the actuator body is a piston(85) which is rigidly fixed to a piston extender rod (87). The volumebetween the bottom of the piston (85) and the top of the lower cap (84)forms a small hydraulic void (86). When fluid is pumped through a hose(98) to the hydraulic fittings (88) and into this void, the pistonextender rod (87) retracts towards the actuator body (82). This removesthe force from the friction block (43) releasing the base sphericaljoint. In a preferred embodiment this small motion also releases theentire arm linkage chain. The hydraulic force acts against a stiff stackof springs (80). The stack is preferably stiff enough that theassemblage acts like a rigid compressive element in the normally lockedlinkage. This embodiment has the advantage of not unlocking the systemwhen the actuator becomes inactive due to loss of fluid pressure, lossof power, or other compromised scenarios.

The pressure to actuate the fluid actuator (21) is produced by a fluidbase unit (20). Contained within the base unit (20) is a master cylinderassembly (90). A cross-sectional view of the master cylinder assembly isshown in FIG. 9. Pressurized gas enters into a port (91) in the outercylinder casing (99) and pushes on a gas piston (92). The force on thepiston is transferred through the connecting rod (93) to the hydraulicpiston (94). Displacement of the hydraulic piston pumps hydraulic fluidout of the hydraulic fittings (95) which connect via hose (98) to theslave fittings (88) shown in FIG. 8.

When the gas pressure is relieved, a spring (96) connected between therigid piston assembly and the outer cylinder casing (99) returns the gasand hydraulic pistons to their base position. A fluid reservoir (97)supplies additional hydraulic fluid to the system as needed. Thehydraulic piston (94) generally has a smaller active area than thepneumatic piston (92) to create much higher pressures in the hydraulicline compared to the pneumatic supply pressure. The hydraulic masterpiston (94) generally has a smaller active area than the hydraulic slavepiston (85) to realize greater forces in the slave actuation systemversus the master system.

To control the gas pressure supplied to the master cylinder assembly(90), the pneumatic system shown schematically in FIG. 10 is used. In apreferred embodiment a high pressure is provided by a miniature gascanister (for example, CO2) that attaches directly to the arm base unit(20). In this manner, the unit is self-contained and does not requireany external plugs. In an alternative embodiment, the high pressuresupply can come from an external pressure source (for instance,compressed air or nitrogen in an operating room). In either case, thehigh pressure supply (100) is regulated down to a fixed pressure with apressure regulator (101). The regulator feeds a 3-way pilot-driven valve(102) that alternatively supplies pressurized air to the master cylinder(90) or vents the master cylinder. The 3-way pilot-driven valve (102) iscontrolled with a 3-way toggle or push button valve (103) that suppliesthe pilot with either high pressure air from the regulator (101), orvents the pilot to the atmosphere. The 3-way toggle or push button valve(103) is responsible for determining whether the arm is locked orunlocked, so it is preferably placed near the end effector (distal end)of the arm to enable one-handed instrument repositioning. A final 3-wayvalve (104) is used to vent the high pressure supply (100) through theregulator (101). This is useful particularly if the high pressure supplyis a miniaturized cylinder, enabling the cylinder contents to be quicklyvented prior to cylinder removal.

As will be clear to those versed in the art, the hydraulic mastercylinder (94) can be actuated by means other than a pneumatic cylinder.For example, the master cylinder can be actuated instead using anelectric motor. The motor can be coupled to a mechanical forcemultiplier system such as a lead screw, eccentric hub, and/or lever toactuate the master hydraulic cylinder (94).

In another embodiment, a bilateral actuator can operate directly usinghigh pressure gas such as CO2 as depicted in cross-section in FIG. 11.For example, a pressurized liquid CO2 canister (110) has a vaporpressure of approximately 850 psi which can provide high force whenvented to a gas piston (111). In a simple embodiment, the canister(s)can be attached directly to the arm, close to the actuator. A pushbutton ‘Y’ valve (112) controls the flow of gas from the attachedcanister. When the ‘Y’ valve is depressed, the cylinder chamber (113)vents to the atmosphere through an exhaust port (116), the canisterinlet (115) is blocked, and there is no pressure exerted on the piston(111). In this position, the actuator applies no force to the upper baserod (42) or base friction block (43) and the arm joints are unlocked.When the ‘Y’ valve is released, a spring (114) automatically returns itto a position such that the vent (116) is blocked and the canister inlet(115) is connected to the cylinder chamber (113). In this position, thepressurized gas exerts force on the piston (111) and expands theactuator against the base friction block (43) and upper base rod (42),causing the arm joints to lock. Note that variations are possible,including embodiments where high-force springs are employed to “reverse”the gas actuator such that gas pressure contracts the actuator insteadof expands it (similar to the hydraulic embodiment in FIG. 8).

FIG. 12 and FIG. 13 show other embodiments for the bilateral actuator.In these embodiments, pressurizing hydraulic fluid delivered via hose(98) through hydraulic fittings (88) causes the arm to lock, anddepressurizing the fluid results in the arm joints unlocking. In FIG.12, two pistons (120)(121) actuate in opposite directions relative to ahydraulic cylinder (122) when the cylinder (122) is pressurized. In FIG.13 a single piston (130) is displaced within a hydraulic cylinder void(132), resulting in expansion of the actuator cylinder body (131)relative to the outer casing (81).

It will be clear to one skilled in the art that a central challenge inthe invention is generating sufficient locking force in a short time andreleasing it quickly. Great care must be taken in selecting suitabledimensions and specifications for each component so that mechanicalstress and strain are within the limits of the materials chosen. Thehydraulic and electric solutions are two prominent classes of solutions.There are other potential mechanisms that can be brought to bear togenerate the required force in a compact and efficient manner.

In an alternate set of embodiments, a cable-actuated roller ball disk(FIG. 14a, b ) can be used to replace one or more pistons in any of thepreviously described actuator embodiments. In this setup, two disks(140) and (141) are coupled together using a central shaft (143). FIG.14a shows the full roller ball disk assembly, and FIG. 14b shows theassembly without the top disk. Each disk has a series of ramped slots(144) (ramp angle θ) that accommodate spherical ball bearings (142).When one disk (140) is rotated relative to the other (141), the balls(142) rotate with respect to the top and bottom ramped slots (144).According to the ramp angle θ, the disk separate apart along the centralshaft (143) as a function of the relative disk rotation. The disks maybe rotated relative to each other using a mechanical cable (146) whichis pulled (e.g. translates) with respect to an outer cable sheath (147).The mechanical cable (146) can be translated relative to the sheath(147) on the arm base unit using a pneumatic cylinder, motor, or othermeans. Because the angle θ can be made arbitrarily small, there is anarbitrarily large mechanical advantage generated by using thismechanism, thus very high forces can be generated to expand the disksrelative to each other. Another advantage of this mechanism is that thehigh-force contact points are rolling contacts, minimizing friction andthus minimizing the energy lost. Another advantage of this mechanism isthat the actuator assembly and mechanical cable and sheath (146) (147)are easily sterilized for medical applications.

In another embodiment of the bilateral actuator (shown in cross-sectionin FIG. 15), a mechanical linkage consisting of two links (150) (151)coupled together with three pins (154) is installed in-line with theupper base rod (42). In this embodiment, large mechanical advantage isachieved as the two links (150) (151) are pushed into alignment towardsthe medial direction. In this embodiment, the medial pushing isaccomplished by an eccentric drive wheel (152) to create furthermechanical advantage for locking the system. The axis of the eccentricdrive wheel (153) may be rotated by a motor shaft, hydraulic means, orother means.

In another embodiment of the bilateral actuator, a set of roller wedges(160) (161) may be used as shown in FIG. 16. A block with two notches(162) houses the tips of two roller wedges and is pushed medially with aforce as shown by the arrow (163). The rolling surfaces of the wedgescan be customized in order to generate a desired mechanical advantage ofblock motion to motion of the upper base rod (42) and a spacer block(164) rigidly fixed to the base friction block (43). The medial force(163) can be applied by any reasonable means including an eccentric hub,hydraulic piston, pneumatic piston, or other means.

FIG. 17(a)-(d) conceptually depict various locking actuation means. FIG.17a represents a bilateral force generator that exerts lockingcompression on the upper base rod(s) FIG. 17b represents a bilateralforce generator that exerts locking tension on the inner rod(s). FIG.17c represents a unilateral force generator that forces the inner rod ina single direction. FIG. 17d represents a locking mechanism that rotatesthe inner rod. These show schematically that the actuation through theupper base rod (42) may be made through any one of a variety of means.These include, but are not limited to, (a) expanding the inner rodlength with a bilateral expanding actuator to cause compression of theupper base rod (42) as described previously in this application; (b)forcibly shortening the inner rod with a bilateral compressing actuatorthat places the upper base rod (42) in tension; (c) forcibly shiftingthe inner rod proximally or distally, thus putting different segments ofthe upper base rod (42) in compression and tension; (d) rotating theinner rod. For each of the upper base rod actuation concepts shown inFIG. 17, the joint locking means must be selected accordingly.

For the concepts depicted in FIG. 17a , as well as FIG. 17c where theupper base rod (42) actuates distally to lock the arm, the centerrotational joint (30) is locked by applying compression forces on theupper base rod (42) as shown in FIG. 6. For the concepts depicted inFIG. 17b , as well as FIG. 17c where the upper base rod (42) actuatesproximally to lock the arm, the center rotational joint (30) is lockedby applying tension forces on the upper base rod (42). FIG. 18a shows across-sectional view of a center rotational joint (30) that actuates viatension force applied to the upper base rod (42). A ramped interface(180) cut into the axle member (185) accommodates a pin (181) attachedto the upper base rod (42) via a bridge member (182). When the upperbase rod (42) translates proximally, the pin (181) pulls the axle (185)towards the base arm segment (7). A nut (66) on the end of the axle(185) pushes the distal slug (61) towards the base arm segment (7),which causes both the distal inner rod (41) to actuate the distaljoints, and the center rotational joint (30) to lock via compressionforce at the friction washer (67). Note that in FIG. 18a , the nut (66)is located on the distal side of the arm (as opposed to previousembodiments where it is on the base side) to accommodate the modifiedfeatures on the base side of the center rotational joint (30).

For the concept depicted in FIG. 17d , the center rotational joint (30)and base spherical joint (31) are locked by applying rotational torqueon the upper base rod (42). FIG. 18b shows a cross-sectional view of acenter rotational joint (30) that actuates via torque applied to theupper base rod (42). An eccentric hub (183) rigidly fixed to the upperbase rod (42) engages a slot (184) cut in the axle member (186). Whenthe upper base rod (42) rotates, the eccentric hub (183) pushes the axlemember (186) towards the base are segment (7). A nut (66) on the end ofthe axle (186) pushes the distal slug (61) towards the base arm segment(7), which causes both the distal rod (41) to actuate the distal joints,and the center rotational joint (30) to lock via compression force atthe friction washer (67). Note that in FIG. 18b , the nut (66) islocated on the distal side of the arm to accommodate the modifiedfeatures on the base side of the center rotational joint (30).

For the concepts depicted in FIG. 17a , as well as FIG. 17c where theupper base rod (42) actuates proximally to lock the arm, the basespherical joint (31) is locked by applying compression forces on theupper base rod (42) as shown in FIG. 5. For the concepts depicted inFIG. 17b , as well as FIG. 17c where the upper base rod (42) actuatesdistally to lock the arm, the base sphere joint (31) is locked byapplying tension forces on the upper base rod (42). FIG. 19 shows across-sectional view of a spherical joint (31) that actuates via tensionforce applied to the inner rod (42). A bridge member (190) connects theupper base rod (42) with a proximal friction cup (191) that contacts theproximal side of the base sphere (31). When the upper base rod (42) ispulled distally, the base sphere (31) is locked by means of compressionbetween the proximal friction cup (191) and the base friction block(43).

While previous examples concentrate on solutions where the internal rodsperform the locking forces, it is also possible to lock the arm jointsby manipulating the base arm segment (7) as shown schematically in FIG.20. In this embodiment, the base upper base rod (42) is continuous andnot acted upon by a locking member. Instead, a force or set of forces(203) are provided to pull two halves (200) (201) of the base armsegment (7) forcibly together. In this example, the actuation means is aring of tapered clamps (202) that are forced inward. This style ofactuation has the same effect on the base joints (30) (34) and centerjoint (30) as the bilateral force generator concept depicted in FIG. 17a, which effectively places the inner rod in compression and the base armsegment (7) in tension. Note that a related embodiment is possible (notshown) where the base arm segment (7) is forcibly placed in tension byan actuator, which has the same effect as the bilateral force generatorconcept depicted in FIG. 17 b.

In the foregoing embodiments, the components inside the central joint(30) may be configured in multiple ways. Several variations are shown inFIG. 21. FIG. 21a shows the primary embodiment of FIGS. 1-4 where thebase slug is pushed laterally away from the center of the joint. FIG.21b shows an alternative embodiment where the base slug is pushedmedially towards the center of the joint. FIG. 21c shows an alternativeembodiment of FIG. 21a where a conical joint interface is used forgenerating increased friction. FIG. 21d shows an alternative embodimentof FIG. 21b where a conical joint interface is used for generatingincreased friction. In the embodiments of FIGS. 18(a) and (c) theactuated inner base rod (42) forces the slugs (60) (61) towards the basearm segment (7), whereas in the scenarios (b) and (d) the inner base rod(42) forces the slugs (215) (216) towards the distal arm segment (8). Ineach case the slug ramp interfaces are selected to achieve a particulardirection of slug motion. In FIG. 21a, b , the rotational jointinterface (210) (211) is flat, where in (c) and (d) the interface isconical (212) (213) at angle θ (214) (217). For conical angles θ (214)(217) in the approximate range 3 degrees to 85 degrees, a rotationallocking advantage is achieved, and less force is required to preventrelative rotation of the base (7) and distal (8) sides of the arm. Theother advantage of the conical angle is that it automatically aligns thejoint together concentrically, minimizing any play or backlash in thejoint. In FIG. 21b , the joint interface is flat and axle (63) end capsprevent the base arm and distal arm from separating. Here, the slugshave large diameter (215) (216) because the primary locking force of thejoint comes from the frictional interface (211) between the slugs. InFIG. 21d , a conical interface retains the two sides of the joint atangle θ (217) generates advantageous friction forces.

In the foregoing embodiments, the actuator (6) was shown positionedbetween the base spherical joint (31) and the center rotational joint(30). In some alternative embodiments, an actuator can be located distalto the base joint (31). In one embodiment shown in FIG. 22a , theactuator is combined with a base unit (220). A first rotatable basejoint (221) and a second orthogonal rotatable base joint (222) enabletwo degrees of rotational freedom proximal to the base rotational joint(34). The clamp to the pole (5) can be a split clamp or internal movingslug.

FIG. 22b shows a cross-sectional view of the combined base actuator(220) and its internal components. This embodiment includes a batterypack 223 and an electric motor (70). A force multiplier is implemented,consisting of a worm (222 w) coupled to the motor shaft and a matingworm gear (222 g). When tightened, the worm gear (222 g) is held inplace axially by a thrust bearing (225) as it pulls a threaded axlemember (224) towards the motor (70). This pull locks the rotatable clampjoint (222) and the rotatable base joint (221). The rotatable base joint(221) locking force is enhanced by friction washer (221 w). The pull onaxle (224) also pulls a ramp surface (224 r) engaging the bottom ofupper base rod (42) thus transferring locking force to the joints distalin the arm.

In the previous embodiments and in commonly practiced prior art, themechanical elements of the arm can experience substantial loads. Severalof the elements must slide under the applied load. The mechanical workdone dragging these elements is not recovered each cycle. Therefore thisenergy must be supplied by a source such as a battery or CO2 cartridge.The magnitude of the lost energy in part determines the size of thebattery, cartridge, and other energy-related elements. In an effort tominimize the lost energy, some or all of the sliding contacts may bereplaced by rolling contacts FIG. 23 schematically depicts this conceptto the details of the center joint (30). Cylindrical rollers (230) and(231) are provided to replace the sliding contacts of the rod interfaces(41 r) and (42 r). The sliding load on the slugs (60) and (61) is alsomitigated by providing rollers (234) and (235). The sliding contact ofthe inner rods (42) and (41) on arm segments (7) and (8) is replacedwith rollers (232) (233) as well.

In another variation (FIG. 24) of the center joint (30), roller wedges(240) and (241) are used to interface between the inner rods (41) (42)and slugs (60) (61). Such wedges may also be used in conjunction withrollers (not shown) as in FIG. 23. In this embodiment, a pair of notches(243) are cut into the upper base rod (42). As the upper base rod (42)is pushed up, a lateral translation occurs to the base slug (60) becauseof the placement of the base roller wedges (241) and notches (243).Through the capped axle member (63), a translation is imparted to thedistal slug (61) which contains a separate notch (244). The motion ofthe distal slug notch (244) rotates the distal rolling wedge (240). Thearc of the distal rolling wedge (240) pushes on the end of the distalinner rod (41) and actuates the distal arm joints. This system has theadvantage of producing a rolling contact between the roller wedge andcompression rod, decreasing frictional losses. In addition this approachallows a customizable mechanical advantage according to the shape of therolling surface. The shape of the rolling surface determines the ratioof motion between the slugs and the inner rods, so customizablemechanical advantage can be achieved. Note that in FIG. 24, the threadedknob (66) effectively acts as the proximal slug (60).

It is important that “slop” in each joint of the arm is minimized suchthat when the arm goes from an unlocked to locked state, theinstrument's position does not change. To minimize this “jump” it iscommon in the art to minimize the clearance at each joint. Each jointmay be pre-loaded with a suitable spring to eliminate the clearance.

To minimize slop in the center rotational joint (30), a spring can beadded in one or more carefully chosen places FIG. 25a shows a spring(250) between the capped axle member (63) and distal slug (61). When thearm is locked (e.g. compressive load is applied to the upper base rod(42) using an actuator (400)), the spring (250) is fully compressed andacts like a rigid element. When the actuator (400) is not in lockingposition, the spring (250) loads the upper base rod (42), distal rod(41), and center joint (30), eliminating all joint clearances in thearm. This also puts a small frictional load on each joint which may beselected to enhance the feel of the arm motion. FIG. 25b shows a similararrangement but a spring (251) is located between the proximal slug (60)and the threaded knob (66). Again, in this arrangement the spring (251)loads the upper base rod (42), distal rod (41), and center joint (30),eliminating all joint clearances in the arm when the actuator is not inlocking configuration.

In some embodiments it is desirable to have preload in some joints andnot preload in other joints. Two example the arrangements illustrated inFIG. 25c and FIG. 25d . In FIG. 25c a spring (252) loads the capped axlemember (63) relative to the distal arm segment (8). This configurationloads the center rotation joint (30) and upper base rod (42), but doesnot load the distal rod (41) and thus does not load the distalrotational joint (33) and distal spherical joint (32). In FIG. 25d thesituation is reversed. A spring (253) located between the threaded knob(66) and the base arm segment (7) loads the center rotational joint (30)and distal rod (41), but does not load the upper base rod (42) and thusdoes not load the base rotational joint (34) and base spherical joint(31).

In other embodiments, the center joint spring can act independently,without putting any pressure on the base or distal rods (41) (42) orslugs (60) (61). One way to achieve this (FIG. 25e ) is to have an outercapped axle (255) that slides relative to an inner dual capped axlemember (256), and a spring (254) that pushes on the dual capped axlemember (256) relative to the distal arm segment (8). This places acompressive load between the base and distal arm segments (7) (8) whichpreloads the center rotational joint (30) without interfering with theslugs (60) (61). An alternate method to achieve this objective is to usemagnets. By way of example, FIG. 25f shows a set of ring magnets (257)that exert attractive forces between the base and distal arm segments(7) (8), thus preloading the center rotational joint (30) withoutinterfering with the slugs or rods.

Alternately or in conjunction with the preloading designs describedabove, the base and distal spherical joints (30) (31) may be pre-loadedwith a spring FIG. 25e depicts a disk spring (258) between the upperbase rod (42) and the base friction block (43). The disk spring (258)preloads the upper base rod (42) when the actuator (400) is not in alocking configuration, thus effectively preloading all joints in the armsimultaneously. Disk springs have the property that they may be pushed“flat” when loaded with high force, and so may act as a rigid elementwhen the actuator (400) is in locking configuration and the arm jointsare locked. To preload only the base spherical joint (31) and baserotational joint (34), FIG. 25h shows another embodiment where anannular spring (259) provides a load between the base friction block(43) and the base spherical joint retainer (35). The upper base rod (42)passes through this spring (259) without transmitting load, so thecentral rotational joint (30) and distal joints receive no preload. Anequivalent design can be applied to preload only the distal sphericaljoint (32) and distal rotational joint (33).

FIG. 6 introduced the detailed features of the central rotational joint(30). One of the functions was to provide a manual mechanical overrideknob (66) in case of actuator failure. FIG. 26a and FIG. 26b showalternate mechanical override methods. In FIG. 26a a threaded coupler(260) connects the base arm segment (7) to the distal spherical retainerbody (35). This effectively provides a method to relieve or applypressure between the actuator unit (400) and upper base rod (42), whichcan lock and release the joints of the arm independent of the actuator(400) state. FIG. 26b shows an alternate threaded coupling (261) locatedbetween the base arm segment (7) and a connecting base arm segment (7a). The purpose of the alternate threaded coupling is to effectivelyextend or retract the overall length of the base arm segment (7), thusmanually locking and unlocking the arm joints independent of theactuator (400) state.

In another embodiment shown in FIG. 27, a double-slotted lockingspherical joint (280) may be used instead of a typical locking sphericalbase joint (31) or distal joint (32). The advantage of this joint (280)is that the range of motion is increased relative to a typical sphericaljoint without having to manually rotate a spherical retainer (36) tomatch a spherical stem (37 s) with a slot (37) (reference FIG. 5). Nowwith reference to FIG. 27, the double slotted locking spherical joint(280) can lock in place by actuating the push rod (287) of the cup part(287 c) relative to the base (286), causing the spherical part (282) tobe clamped between the outer casing (283) and cup part (287 c), thuslocking the sphere (282) and sphere stem (281) with respect to the base(286). A ridge feature (283 r) on the outer casing (283) engages a lipfeature (2861) on the base (286), connecting the outer casing (283) withthe base (286) with a first rotational degree of freedom. The lower slot(2841) provides clearance for the push rod (287). An upper slot (284 u)allows the sphere stem (281) to rotate substantially orthogonal to thefirst rotation. Each slot (284L) (284 u) is cut sufficiently long suchthat the spherical stem (281) and push rod (287) have a large range ofmotion before contacting the edges of the slots.

Note that in all of the locking systems described herein, it is possibleto “partially” actuate the system to produce an intermediate frictionstate between “fully locked” and “fully released”. In hydraulic andpneumatic actuation systems, this can be achieved by applying variablepressure to the hydraulic or pneumatic cylinders. In the mechanicalactuation systems, this is achieved by partially deploying the motor ormechanical system. The partially locked state can be used to enable finepositioning of the arm, as adding resistance to the arm joints makesfine motions of the arm easier to control by hand. In one workflow, whenthe instrument being held by the arm is close to its final position, thearm can change from fully unlocked to partially locked. After precisionadjustments of the instrument using the partially resistive state of thearm, the arm can be fully locked into final position with full force.

As previously mentioned, arm lock/unlock button or switch (12, FIG. 1)is preferably placed near the distal end of the arm to enable one-handedinstrument manipulation and unlocking/locking. The button or switchalternatively be placed on the floor (foot pedal), near the proximalbase of the arm, or other locations. Another interesting place to putthe button is on or near the center rotational joint (30). This way, theuser is sure to be touching the center rotational joint (30) of the armwhen unlocking the arm to prevent it from collapsing due to gravitywhenever the arm is unlocked.

In many medical environments, sterilization of equipment is oftendesirable. In some arm embodiments it is feasible to sterilize theentire arm system, such as the direct CO2-powered embodiment shown inFIG. 11 or embodiments actuated with cable-actuated roll ball disks(FIG. 14). In other embodiments, it is desirable to not expose certainelements of the arm (hydraulic fluid, seals, etc.) to the harshsterilization process. FIG. 28a and FIG. 28b show two alternativemethods to keep the arm sterile in the operating environment. In FIG.28a the entire arm including actuator (400), base arm segment (7),distal arm segment (8), and base unit ((1) or (20)) is draped with athin sterile sleeve (290). The drape can terminates at the sterileinstrument holder (9) at a drape interface (not shown), and theinstrument (10) can be sterile. In FIG. 28, only the base unit ((1) or(2)) and actuator locking mechanism (400) are covered with a drape(291). The portion of the arm distal to the actuator (400) including thebase arm segment (7), distal arm segment (8), and instrument holder (9)can be sterilized using steam, chemicals, or other methods. Theembodiment of FIG. 28b is desirable because the part of the arm that isclosest to the operating site is not draped, thus remains very compactand slender where space is critical. This embodiment (FIG. 28b ) relieson the fact that the distal portions of the arm can be detached from theactuator (400).

A screw thread, such as shown in FIG. 26a and FIG. 26b may be used fordetachment of the distal portion of the arm from the actuator. FIG. 29aand FIG. 29b detail another embodiment of a detachment mechanism betweenthe distal arm portions and proximal base that is well suited for a basearm drape (291). A series of tabs (301) on the base arm segment (7)matches a series of slots (302) on the actuator unit (400). The base armsegment (7) is pushed towards the actuator (6), and once the tabs (301)clear the slots (302), the base arm segment (7) and actuator (400) arerotated relative to each other. Rotation is allowed until the pin (303p) on the spring-loaded push release lever (303) mates to the notch (301n) on one of the tabs (301). At this point, further rotation isprevented and the actuator (400) and base arm segment (7) are lockedtogether. It is advantageous to retract the actuator extension (6 e) sothat excessive force does not need to be deployed in the mating processbetween the actuator (400) and the base arm segment (7). To release theactuator (400) from the base arm segment (7), the release tab (303 r) ispushed so that the pin (303 p) releases from the notch (301 n). The basearm segment (7) and the actuator (400) are then rotated relative to eachother such that the tabs (301) and slots (302) line up, and subsequentlythe base arm segment (7) can be extracted from the actuator (400). Inthis embodiment, the sterile drape (291) may be taped (300) to the basearm segment (7) above the distal tabs (301), prior to attaching the basearm segment (7) to the actuator (400) as seen in FIG. 29b . The steriledrape (291) may also be attached to the base arm segment (7) or actuator(400) by other means.

Other than the ability to sterilize the portion of the arm distal to theactuator (400), there are other interesting aspects of having the distalportions of the arm removable from the actuator (400) as shown in FIG.28b and FIG. 29. The portion of the arm distal to the actuator (400)comprises only mechanical parts (tubes, rods, slugs, joints, etc.), andthus can be fabricated out of disposable plastic materials for one time(or limited time use) in the operating room. This can be useful incertain surgical procedures where it is desired to dispose of the distalportions of the arm after each use while retaining/reusing the actuator(400) and base (1) (20) that provide the locking and unlocking power.Another interesting aspect is that distal arm linkages of differentlengths and sizes can be attached to the same actuator (400 and base(1)(20), enabling users to customize the arm system for a particularsurgical application.

It is also possible for portions of the arm distal to the actuator (400)to be radiolucent. This is particularly useful in medical applicationswhere x-ray imaging modalities may be used in conjunction with aprocedure where instruments (10) must be held steady. Materials such ascarbon fiber, which do not interfere with x-rays, can be used tofabricate the portions of the arm distal to the actuator (400). Theactuator (400) and parts proximal to the actuator may still containmetallic or high density components, since these components are notclose to the imaging target (and instrument being held) and thus willnot interfere with x-ray imaging. For example, in FIG. 28b and FIG. 29,the entire portion of the arm distal to the actuator (400) could be madeof radiolucent material choices. Alternatively, the center rotationaljoint (30) could contain radiopaque materials, and only the distal armsegment (8), distal spherical joint (32), distal rotational joint (33),instrument holder (10), and other components distal to the centerrotational joint (30) could be made of radiolucent materials.

In some embodiments it may be useful to include a counter-balance tocompensate for at least some of the arm's weight and/or the weight ofthe instrument (10). This helps relieve the user from struggling againstthe weight of the arm and/or instrument when positioning and maneuveringthe instrument. The general problem is taking stored energy from aspring to compensate for a change in potential energy as the position ofthe arm changes. While a full counter balance design is possible thatcompensates for the entire weight of the arm and/or instrument, asimpler and still useful implementation is to counter balance only theproximal arm linkage (335), including the actuator (400) and the basearm segment (7). The reason is that the nominal arm embodiments (FIGS.1-4) have at least 7 degrees of freedom which means that for anarbitrary placement of the instrument (10) in 3D space, the centralrotational joint (30) is still freely able to swivel. Adding a counterbalance to compensate for the weight of the proximal arm linkage (335)can enable the proximal arm linkage (335) and central rotational joint(30) to “float” in an arbitrary position in space and not “fall” underthe weight of gravity when not being supported by a hand.

Referring to FIG. 30, one method of counterbalancing the proximal armlinkage (335) is to use a set of compression springs (330) straddlingthe base spherical joint (31). To accommodate the base spherical joint(33) rotation about the pole (5) axis, a means must be provided toposition the springs (330) as the joint (33) rotates. This is depictedby a ring (332). Not shown are the elements needed to rotate the ring asthe arm moves.

Another novel counter balance means is to put a compressive springelement (340) around the pole (5) as depicted in FIG. 31. The bottom ofthe spring (340) pushes against a lower ring (341) fixed to the pole. Anupper ring (342) is free to translate up and down on the pole,compressing the spring (340) according to the spring's displacement. Thespring (340) is compressed as a direct result of the proximal armlinkage (335) deviating from vertical. The angular motion of theproximal arm linkage (335) is conveyed by 6 link members (344) connectedto a ring (343) attached to the proximal arm linkage (335) above thebase spherical joint (31). This set of links (344) forms an octahedronwhich compensates for gravity on the proximal arm linkage (335) basedthe angle of the base spherical joint (31) with respect to vertical.

It is a well-known problem in surgery that applying retraction forcesfor long periods of time can result in tissue damage or necrosis.Therefore, it is suggested that retractor blades are periodicallyreleased throughout the surgical procedure. However, with existingretraction systems, release of retractor blades takes significant timewhich is very costly in the operating room. The system in FIG. 32 whichleverages the locking arm technology herein addresses this problem sinceeach retractor blade can be independently released and repositionedwithin a matter of seconds. In one embodiment of the retraction system,one or more arms are deployed (350) to hold one or more retractor blades(352), each arm with an independent lock/unlock button or switch (351)preferably located near the distal end of the arms. It is advantageousfor each arm (350) to be deployed from the superior or inferiordirection of the table (3) as shown so that the surgeon (353) andassistant (354) have ample space to operate. More than one arm (350) canbe attached to a single pole (5), and multiple arms can share the samebase unit (1)(20) as applicable.

In one embodiment of the retraction system shown in FIG. 35, anelectronic system controller (not shown) alerts the user to move eachrespective arm (350) after a certain period of time has elapsed (forexample, 20-30 minutes). The alert can be in the form of a sound,blinking light, steady light, or other means. Each arm can have one ormore LED lights attached to it (355), preferably co-located with thelock/unlock button (351). The controller can change the light (355)state, e.g. from green to red or from off to on, when retraction timefor each respective arm has reached a threshold. Once the arm (350) isreleased, repositioned, and relocked, the controller can reset the timerand light state (e.g. red to green or on to off). In another embodiment,there may be force sensors, blood flow sensors, or other sensorsattached to the arms (not shown) that indicate retraction force ortissue state. Once these sensors indicate that the tissue is in danger(e.g. low blood flow, or excessive force over a certain period of time),the controller can alert the user to move the retractor blade (352)using means described above. Once moved, the arm (350) alerts thecontroller that the tissue is safe again, and monitoring/timers canreset. Note that the retraction alert system described herein can alsoapply to retraction systems that do not utilize the automatic lockingarm described in this application.

In another embodiment of a locking arm system (FIG. 36), two or morearms (360) are used in parallel to hold the same instrument (10). Two ormore arms in parallel significantly increases the overall stiffness ofthe arm system, further minimizing any motion of the instrumentation(10) being held under load. Two arms can be controlled with the sameactuation button or switch (361), locking and unlocking both arms (360)simultaneously for ease of use. In the particular scenario shown in FIG.36, two arms can hold a single tube (362) for pedicle screw placementduring spine surgery to ensure maximum strength and stiffness duringscrew drilling, tapping, and insertion.

Modification of the above-described assemblies and methods for carryingout the invention, combinations between different variations aspracticable, and variations of aspects of the invention that are obviousto those of skill in the art are intended to be within the scope of theinvention disclosure.

1-53. (canceled)
 54. A lockable support assembly comprising: a base armhaving a lower end and an upper end; a distal arm having a proximal endand a distal end; a center joint directly or indirectly linking theupper end of the base arm to the proximal end of the distal arm; a lowerjoint at the lower end of the base arm; an upper joint at the distal endof the distal arm; and a powered locking actuator disposed within thebase arm between the lower end and the upper end, the powered lockingactuator configured to simultaneously engage the lower joint, the centerjoint, and the upper joint to deliver locking forces to the lower joint,the center joint, and the upper joint.
 55. An assembly as in claim 54,further comprising a latching mechanism that prevents the poweredlocking actuator from disengaging upon loss of power to the poweredlocking actuator.
 56. An assembly as in claim 55, wherein the latchingmechanism comprises a non-backdrivable lead screw mechanism whichmaintains its position when power is lost.
 57. An assembly as in claim54, wherein the powered locking actuator comprises a force generatorcomprising a motor which is coupled by a lead screw to deliver forces tothe center joint, the lower joint, and the upper joint.
 58. An assemblyas in claim 54, wherein the base arm is separable from the poweredlocking actuator to allow removal of the base arm, distal arm, andcentral and upper joints to permit sterilization or replacement of thebase arm, distal arm, and central and upper joints.
 59. An assembly asin claim 54, further comprising a lock/unlock button or switch disposednear a distal end of the distal arm to enable one-handed instrumentmanipulation and unlocking/locking.
 60. A lockable support assemblycomprising: a base arm having a lower end and an upper end; a distal armhaving a proximal end and a distal end; a center joint directly orindirectly linking the upper end of the base arm to the proximal end ofthe distal arm; a lower joint at the lower end of the base arm; an upperjoint at the distal end of the distal arm; and a powered lockingactuator configured to simultaneously engage the lower joint, the centerjoint, and the upper joint to deliver locking forces to prevent relativemotion of the base arm and the distal arm; wherein the powered lockingactuator is disposed within the base arm between the lower end and theupper end.
 61. An assembly as in claim 60, wherein the powered lockingmechanism comprises a force generator which transmits a locking forcethrough the base arm and the distal arm to lock the joints.
 62. Anassembly as in claim 61, wherein the force generator comprises a motorwhich is coupled by a lead screw to deliver forces to the center, lowerand upper joints.
 63. An assembly as in claim 60, further comprising alock/unlock button or switch disposed near a distal end of the distalarm to enable one-handed instrument manipulation and unlocking/locking.64. An assembly as in claim 60, wherein at least some of the lowerjoint, the center joint, and the upper joint are biased to reduceclearances in the respective joint or powered locking actuator in theabsence of locking forces to prevent an unintended change of armposition as the powered locking actuator engages the joints.
 65. Alockable support assembly comprising: a base arm extending along a firstlongitudinal axis between a lower end and an upper end; a distal armhaving a proximal end and a distal end; a central joint directly orindirectly linking the upper end of the base arm to the proximal end ofthe distal arm; a lower joint at the lower end of the base arm; an upperjoint at the distal end of the distal arm; and a powered lockingactuator disposed within the base arm at a location between the lowerjoint and the central joint, the locking actuator configured to controllocking of the lockable support assembly by delivering locking forces tothe lower joint, to the central joint, and to the upper joint.
 66. Thelockable support assembly of claim 65, wherein each of the centraljoint, the lower joint, and the upper joint include a locking mechanismto receive the locking forces delivered by the power locking actuatorand lock respective joints in response to receiving the locking forces.67. The lockable support assembly of claim 65, wherein the power lockingactuator includes a bi-lateral force generator to simultaneously deliverthe locking forces to the lower joint, the central joint and the upperjoint.
 68. The lockable support assembly of claim 67, wherein thepowered locking actuator further comprises an upper base rod whichtransmits the locking force from one side of the bilateral forcegenerator to the central joint and a distal rod which transmits thelocking force from the central joint to the upper joint.
 69. Thelockable support assembly of claim 68, wherein the powered lockingactuator further comprises a lower base rod which transmits force froman opposite side of the bilateral force generator to the lower joint.70. The lockable support assembly of claim 65, wherein the central jointcomprises a rotational joint having an axle joining the upper end of thebase arm to the proximal end of the distal arm and wherein an interfacesurface at the upper end of the base arm frictionally engages aninterface surface on the proximal end of the distal arm such that thepowered locking actuator drives the interface surfaces together toprevent relative movement of the arms.
 71. The lockable support assemblyof claim 70, wherein the rotational joint further comprises a firstinclined surface which receives force from the upper base rod and asecond inclined surface which transmits force to the distal rod, whereinthe aligned surfaces are coupled by the axle which both (1) locks theinterface surfaces together; and (2) translates the second inclinedsurface in response to the upper base rod engaging the first inclinedsurface.
 72. The lockable support assembly of claim 65, wherein thelower joint and the upper joint each comprise spherical joints includinga friction block which is coupled to a bilateral force generator to lockthe spherical joints when the generator generates a locking force. 73.The lockable support assembly of claim 65, wherein the power lockingactuator comprises a bilateral force generator which transmits a lockingforce in one axial direction to the lower joint and in an opposite axialdirection to the central joint and the upper joint, the bilateral forcegenerator including a lead screw driven by a motor and a follower whichtravels over the screw.